An ion-sensitive field-effect transistor (ISFET), which is well known as a (bio-)chemical sensor, is utilised as transducer in a hybrid sensor module for the detection of four physical parameters (flow velocity, flow direction, diffusion coefficient of ions and liquid level). The experimental results of testing of the developed multi-parameter hybrid module in different sensor arrangements are presented. A novel ISFET-based liquid-level sensor as well as a "time-of-flight"-type ISFET-array-based flow-velocity sensor employing the in-situ ion-pulse generation are introduced and realised. An influence of the counter ions on the behaviour of the ISFET-based flow-direction sensor is discussed, too. (C) 2003 Elsevier Science Ltd. All rights reserved.